{
    "type": "record",
    "name": "main",
    "fields": [
        {"name": "a", "type": "long"},
        {"name": "b", "type": {
            "type": "record",
            "name": "sub1",
            "fields": [
                {"name": "a", "type": "string"},
                {"name": "b", "type": "double"},
                {"name": "c", "type": "double"}
            ]
        }},
        {"name": "c", "type": "string"}
    ]
  }